1. Field of this Invention
This invention relates to a process for the production of cyanopyridines by reaction of monoalkyl pyridines with oxygen or air and ammonia in the gaseous phase in the presence of a catalyst, and further relates to the use of a specific catalyst which unexpectedly produces greatly improved results.
2. Prior Art
The production of cyanopyridines by reaction of alkyl substituted pyridines with ammonia and oxygen at elevated temperatures in the gaseous phase with the help of (in the presence of) catalysts.
Several different catalysts have been used in the subject reaction. For example, in U.S. Pat. No. 2,510,605 a vanadium-molybedeum-phosphorus oxide containing catalyst was used and the ammoxidation (the subject reaction) was carried out at 400.degree.-500.degree.C. However the yields and selectivity are bad.
According to the process of U.S. Pat. No. 2,592,123 a molybdenumoxide catalyst is used in the subject reaction at temperatures of over 410.degree.C. Beside the disadvantages of poor yields, the catalyst also quickly loses its activity and must be frequently reactivated.
U.S. Pat. No. 2,839,535 uses a special vanadium oxide catalyst, which is applied to pre-treated Al.sub.2 O.sub.3. The patent teaches that it is of the utmost importance that the Al.sub.2 O.sub.3 be pretreated at temperatures of 1,150.degree. to 1,400.degree.C., otherwise poor yields are obtained. Beside this disadvantage, the catalyst becomes inactive in the course of time during the reaction and must be regenerated.
According to U.S. Pat. No. 3,297,587 the ammoxidation must be carried out with the use of borophosphate catalysts activated with compounds of the metals bismuth, molybdenum, vanadium, iron or cobalt. This process too was not satisfactory since these catalysts are partly split into boric acid and phosphoric acid during the reaction.
German (published) application No. 1,770,841 uses tin-phosphate catalysts activated with molybdenum, bismuth, vanadium, iron or cobalt. Disadvantages of the process of the German Application publication consists of, on the one hand in fact, that these special catalysts must first be produced, and, on the other hand in the fact that, as temperatures of 300.degree. to 700.degree.C. are used, the phenomena of decomposition has already occurred.